Post subject: Greenish-red, yellow-blue, and the color yellow
Posted: Wed Oct 05, 2011 7:28 pm
Platinum Member
Joined: Tue Jun 03, 2008 4:40 pm Posts: 2667 Location: South Dakota
I found this wrirren by Bob Berman..never really thought about it this way
.............."Colors are simply waves of different lengths and the perception of color comes from the mixture of red, blue, and green. Those are lights primary colors. The true colors. They are totally different from the primary colors of paint.
The bright light architecture has plenty of quirks. We see yellow only when we receive an equal dose of green and red light. You would think seeing red and green light would give us the sensation of “greenish-red but no such color exist. Yellow is our “greenish-red” even if it bears no resemblance to either hue.
This contrast with our subjective experiences of sunlight’s other primary colors. We do indeed percieve reddish-blue as purple and greenish-blue as aqua or cyan. Yet thanks to our eye-brain wiring system, we cannot gain the subjective experience of a reddish-green or a yellow-blue, nor even imagine it."...................... Bob Berman
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Post subject: Re: Greenish-red, yellow-blue, and the color yellow
Posted: Fri Oct 07, 2011 2:03 pm
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Joined: Thu Jan 05, 2006 4:27 pm Posts: 1750
This was the subject of Brians last chat (The one we couldn't save or copy) That was a real pity because it was something I had never encountered before and was a Fascinating subject. Unlike paint it's colour subtraction rather than colour addition. So if you shine a blue and a yellow light at the same spot on the wall you don't get green...you get white.
Post subject: Re: Greenish-red, yellow-blue, and the color yellow
Posted: Fri Oct 07, 2011 5:59 pm
Gold Member
Joined: Fri Oct 12, 2007 10:22 pm Posts: 1117 Location: Virginia
I was trained as an artist and I have a terrible time trying to reconcile color between fine arts and gemology (not just the names ). I think maybe it's because of this difference. (Or my eyes... )
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Post subject: Re: Greenish-red, yellow-blue, and the color yellow
Posted: Sat Oct 08, 2011 7:14 pm
Gemology Online Veteran
Joined: Thu Sep 25, 2008 10:33 am Posts: 840 Location: Mars PA
In the world of gemstones there are two examples of mixing red and green to make yellow that are quite exciting.
Alexandrite's color change is enhanced because the mixing of it's two colors, as you would see under mixed light conditions, is yellow. Yellow mixed into and dominated by red or green does not produce the continuous color mixture that we perceive when, for example, you would have a color changer from blue to green. I have tourmaline, that I believe to be cuprian, that has a strong shift from blue to green, but much of the time it is blue green because it is difficult to get "pure" white light that isn't mixed in modern homes. I morn the departure of incandescent lights because they can bring out fantastic colors in some tourmaline. Paraiba tourmaline definitely fires up under incandescent.
The other pink/green mixture that I like is in tourmaline. Nigeria has produce quite a bit of this lately. You think you have a tri-color with pink, green and yellow in pastel tones, but you really have only pink and green. As the stone is turned you get to see color change caused by different mixtures of pink and green. It is pretty neat.
Finally like all spectral colors, violet, blue, green, yellow, orange and red, yellow has it's own own set of wavelengths and does not have to come from mixing green and red. It is certainly true that mixing the primary colors, both the set of additive and subtractive, can produce all the colors we can perceive.
Post subject: Re: Greenish-red, yellow-blue, and the color yellow
Posted: Wed Oct 19, 2011 10:07 pm
Gemology Online Veteran
Joined: Fri Jan 27, 2006 12:27 pm Posts: 764 Location: Western NY
I can't add anything to the science, but this discussion reminds me of a comment Tom Stoppard made in one of his plays: “The colours red, blue and green are real. The colour yellow is a mystical experience shared by everybody.” (from Rozencrantz & Guildenstern Are Dead)
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